As portable electronic devices become more compact, and the number of functions performed by a given device increase, it has become a significant challenge to design a user interface that allows users to easily interact with a multifunction device. This challenge is particular significant for handheld portable devices, which have much smaller screens than desktop or laptop computers. This situation is unfortunate because the user interface is the gateway through which users receive not only content but also responses to user actions or behaviors, including user attempts to access a device's features, tools, and functions. Some portable communication devices (e.g., mobile telephones, sometimes called mobile phones, cell phones, cellular telephones, and the like) have resorted to adding more pushbuttons, increasing the density of push buttons, overloading the functions of pushbuttons, or using complex menu systems to allow a user to access, store and manipulate data. These conventional user interfaces often result in complicated key sequences and menu hierarchies that must be memorized by the user.
Many conventional user interfaces, such as those that include physical pushbuttons, are also inflexible. This is unfortunate because it may prevent a user interface from being configured and/or adapted by either an application running on the portable device or by users. When coupled with the time consuming requirement to memorize multiple key sequences and menu hierarchies, and the difficulty in activating a desired pushbutton, such inflexibility is frustrating to most users.
In particular, when a conventional user interface on a portable device is used to display a portion of an electronic document or of a list of items, a user may not be able to tell the position in the document or list of the displayed portion. The user also may not be able to tell what fraction of the document or list corresponds to the displayed portion. Lacking this knowledge, the user may find viewing and navigating the document or list to be confusing and frustrating. In some portable devices, scroll bars are used to indicate the position in the document or list of the displayed portion. But scroll bars are fixed user interface features that take up valuable display screen area on an already small display screen.
Accordingly, there is a need for portable multifunction devices with more transparent and intuitive user interfaces for navigating portions of electronic documents and/or lists of items that are easy to use and that do not reduce the screen area available for the display of documents, lists, and other content. Such interfaces increase the effectiveness, efficiency and user satisfaction with portable multifunction devices.